The present invention relates to operating channel/insufflation port assemblies which are useful in a technique for minimally-invasive invagination of the esophagus at the gastroesophageal junction described in the above referenced co-pending patent application, Ser. No. 608,339, the complete disclosure of which is hereby incorporated by reference. The operating channel/insufflation port assemblies described and claimed herein are useful for other minimally-invasive techniques as well in which an operation is performed percutaneously with remotely operable instrumentation through an operating port while a positive internal pressure is maintained during the operation.